In the manufacture of semiconductor devices such as various semiconductor elements and semiconductor integrated circuits including bipolar transistors and insulated gate field effect transistors (MOS transistors) in the related art, in order to form a contact between semiconductor and metal, a metal layer has usually been deposited on a surface of a semiconductor to receive heat treatment by maintaining them at a predetermined temperature in an annealing furnace in an atmosphere of inert gas or the like for a certain time so that an electric characteristic between the semiconductor and the metal has been improved to obtain an excellent ohmic characteristic (see Patent Document 1, for example).
When gold (Au) is formed as a contact layer for silicon (Si), it is usual to heat treat them in an inert gas to a temperature higher than a Si/Au eutectic temperature of 373° C. to obtain an excellent contact. It is possible to deposit aluminum (Al) on silicon and then deposit a plurality of metal layers. In this case, it is usual to perform heat treatment at about 450° C. to improve a Si/Al contact after depositing the plurality of metal layers on the silicon.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 6-120165